The secrets to bull barrels are as follows.
1. The thicker barrel helps to minimize barrel whip (harmonics).
2. The thicker barrel will not heat up as fast due to heat dissipation. The colder the barrel, the less movement whip it will have.
3. The open muzzle allows for a cleaner bullet exit blast path.
4. The open muzzle allows the muzzle to be cleaned of any muzzle face fouling that can deviate the bullet exit and gas escape path.
Any modifications that will change the characteristics of the barrel may not be for the best. By adding a muzzle device, you will run into problems with keeping the crown clean, and the possible influence that the device will add to the barrel harmonics. On thinner barrels, an end weight can be added to minimize the end whip, but on a barrel that is all ready heavily weighted/stiff, the added weight may just be over-kill.
Also, since the 223 round has very little recoil, and the rifle is heavily weighted, the use of a brake in not needed. Knowing this, the only other reason would be to add a muzzle protector. If this were the reason for the device, then I would thread the barrel, and add a decorative type sleeve that would require minimal barrel reduction for threading. And, the design to be an open design to allow full access to the barrel crown face for cleaning.
Food for thought.